1. Field of the Invention
The present invention relates to a gas compressor for use in an automotive air conditioning system or the like and, in particular, to a gas compressor with improved cooling capacity.
2. Description of the Related Art
FIGS. 9A and 9B shows a conventionally known vane rotary type gas compressor. In the conventional gas compressor shown, a refrigerant gas is compressed in a cylinder 4 of a gas compressor main body 2. The refrigerant gas compressed is sucked from a suction port 17 of a front head 3 constituting a refrigerant guide passage into the cylinder 4 by way of a suction chamber 150 inside the front head 3 and a side block suction hole 16.
As shown in FIGS. 10A to 10E, the above gas compressor of the conventional construction adopts a structure in which the suction chamber 150 is defined by a hollow portion 14 inside the front head 3 and an outer surface 5a of a side block 5 opposed thereto. Thus, due to the fact that the suction chamber 150 has a structure as a “chamber” for temporarily storing the refrigerant gas and that the suction chamber 150 has a large number of protrusions and recesses due to a plurality of reinforcing ribs 20 protruding from the outer surface 5a of the side block 5, etc., the gas compressor has a problem in that it involves a deterioration in cooling capacity.
That is, the presence of protrusions and recesses in the suction chamber 150 leads to an increase in the frictional resistance of the refrigerant gas passing through the suction chamber 150, resulting in pressure loss of the refrigerant gas. Thus, the pressure of the refrigerant gas at the inlet of the cylinder 4, that is, the pressure of the refrigerant gas immediately before its suction into the cylinder 4 by way of the suction chamber 150 and the side block suction hole 16, becomes excessively low as compared with the pressure of the refrigerant gas on the upstream, suction port 17 side. Due to this reduction in pressure of the refrigerant gas, the density of the refrigerant gas sucked into the cylinder 4 is reduced, with the result that the amount of refrigerant gas sucked into the cylinder 4 decreases, resulting in a deterioration in the cooling capacity of the gas compressor.
Further, the longer the refrigerant gas stays in the suction chamber 150 described above, the more heat it takes from the front head 3, the parts of the side block 5, etc. As a result, the temperature of the refrigerant gas rises to an excessive degree. Furthermore, the higher the temperature of the refrigerant gas, the lower the density of the refrigerant gas.
In particular, when the gas compressor is operated at a low rotating speed, the flow velocity of the refrigerant gas is low, so that the refrigerant gas is liable to stay within the suction chamber 150, and the quantity of the heat that the refrigerant gas takes from the front head 3, the parts of the side block 5, etc. increases, which leads to a further increase in the temperature of the refrigerant gas, resulting in a substantial deterioration in cooling capacity.
Incidentally, instead of the suction chamber 150 in the form of a “chamber” as described above, some conventional gas compressors adopt a suction passage in the form of a “passage” (See, for example, JP 58-135396 A and JP 9-158868 A).
The gas compressor as disclosed in JP 58-135396 A is equipped with one suction passage (as indicated at 30 in FIG. 3 of the publication) extending spirally from a suction port (as indicated at 32 in FIG. 3 of the publication). Opened respectively at a midpoint and a terminal of this spiral suction passage are two side block suction holes (as indicated at 34a and 34b of the drawing). As a result, the distance from the suction port constituting the suction start point to the final side block suction hole situated at the terminal end of the suction passage is inevitably rather long. Before it reaches the side block suction hole at the terminal end, the refrigerant gas takes a large quantity of heat from the side block (indicated at 18 in the drawing), etc., resulting in an increase in the temperature of the refrigerant gas and, consequently, a reduction in the gas density, which is quite likely to lead to a deterioration in cooling capacity.
In the gas compressor as disclosed in JP 9-158868 A, there is formed a suction passage (indicated at 11 in FIG. 2 of the publication) by utilizing an end surface of a cam ring (indicated at 1 in FIG. 1 of the publication) corresponding to the cylinder 4 shown in FIG. 9A of the present application. More specifically, a passage-like hollow portion is formed in the inner side surface of a rear head (indicated at 6 in FIGS. 1 and 2 of the publication) opposed to the end surface of the cam ring (indicated at 1 in FIG. 1 of the publication), and a suction passage is defined by the passage-like hollow portion and the end surface of the cam ring. Thus, due to the presence of the suction passage, it is impossible to secure to a sufficient degree the sealing surface on the cam ring end surface side. The shortage of sealing surface is likely to cause what is called an inner leakage, in which a compressed high-pressure refrigerant gas is leaked from the inner side of the cam ring to the low-pressure side. As a result of this inner leakage, the amount of refrigerant gas sucked in is reduced, which is quite likely to lead to a deterioration in cooling capacity.
Also in the above-described suction passage structure utilizing the end surface of the cam ring, it is possible to secure a sufficient passage sectional area for the suction passage and reduce the suction resistance of the refrigerant gas either by forming the suction passage deep or by enlarging the width of the suction passage. However, in the case in which the suction passage is formed deep, it is necessary, from the viewpoint of the strength of the rear head, to form the rear head thick accordingly. Further, in the case in which the width of the suction passage is enlarged, it is necessary to radially expand the rear head and the cam ring in order to secure the requisite sealing surface on the cam ring end surface side. Thus, in either case, an increase in the size of the gas compressor is inevitable.